This invention relates to a workpiece changing mechanism for a numerically controlled lathe in which a workpiece gripper for transferring workpieces from a workpiece transfer station to the work fixture of the lathe is provided in a tool centering recess of a turret of the lathe.
A workpiece changing mechanism of this type is known from German Auslegeschrift No. 1,148,840 in which the rotational axis of the turret is at an angle of 90.degree. to the rotational axis of the spindle. The workpiece gripper is located in a radial tool centering recess of the turret. Therefore, the workpieces are transferred by the workpiece gripper by a 180.degree. rotation of the turret in the longitudinal direction of the lathe. Although this makes it possible to locate the workpiece transfer station well beyond the turnings area without long travels of the saddle being necessary for changing the workpiece, considerable time is required for the 180.degree. rotation of the turret. Moreover, this arrangement only makes it possible to load or transfer short shafts or chucks of small size.
In modern lathes, the turret is generally axially parallel to the spindle, so that a maximum number of tools can be set in the turret through axial tool centering recesses.
If it were desired to equip such a lathe with a workpiece changing mechanism in which a workpiece gripper had to be fitted in the turret, the workpiece would not be conveyed out of the turnings area by a rotation of the turret. Therefore, the saddle would have to be moved to a workpiece transfer station located outside the turnings area, which would once again take too much time.
Hitherto, the arrangement of the workpiece transfer station between the turnings guard and the movement path of the turret in order to reduce the necessary time has not been considered because in this area the space conditions are very unfavourable and the transfer of the workpiece would have to take place at the point accessible to turnings during the machining process. It must also be ensured that the workpiece transfer station and the associated devices for supplying and removing the workpieces must not impede the visibility of the lathe operator.